1. Field of the Invention
This invention pertains to transmission line terminators and in particular to nonlinear transmission line terminators that are adaptable to terminate signals having different types of logic originations.
2. Description of the Prior Art
In the past, in some high speed digital applications, ordinary passive terminations (resistors) have been used. These terminators reduce or remove the impedance discontinuities and allow the signals to achieve their final values in minimum time, while increasing the power dissipation. These termination resistors must, however, be both matched to the wave impedance of the system and also compatible with the steady-state characteristics of the signal origination. This terminator may be satisfactory for a given type of logic originator. However, it is not adaptable to termination of signals originated by different types of logic circuitry.
In other signal and transmission environments, a nonlinear termination has been successfully used. It is referred to as "nonlinear" because its current versus voltage curve is not linear. It is also referred to as an "active" termination because it is most often implemented with the aid of active devices such as transistors instead of only resistors.
The major limitation to these prior art implementations is that their application is restricted to particular areas. That is, they are designed for specific signal levels. The circuit designed to work with ECL origination, for example, is not at all suited to TTL. This invention is capable of interfacing with many different types of origination logics.